The present invention relates generally to a method and apparatus for temporarily reforming or deforming the lip portion of a resinous seal so that the seal may be readily installed in an intended application.
There are many uses for seals having lips which are made entirely or primarily of a fluorocarbon resin, such as Teflon (TFE), filled Teflon, or some chemically generally similar polymer, owing to TFE having the chemical resistance, heat resistance, abrasion resistance and other favorable characteristics. Such seals have drawbacks, however, such as lack of resiliency in the lip. Consequently, such seals are ordinarily made by utilizing a lip of the polytetraethylene (PTFE) or like material, entrapped between a seal having a metal outer case and a metal inner case, with the inner case being held in position by being crimped by the outer case. The lip portion of the seal is thus held between radially extending elements of the inner and outer casings. In other instances the resinous lip is bonded directly to the metal cases. In still other instances, the TFE lip is bonded to a rubber gasket or the like which is then bonded to a metal case.
In making Teflon or the like seals, there has been one problem which has confronted the industry for some time. In order to fit these seals over the application, usually a rotary shaft or the like, it is necessary to mechanically “bellmouth” or otherwise distort the seals to at least the diameter on which they will become effective upon installation. The problem with the usual way of bellmouthing these seals is that the apparatus required to perform the bellmouthing operation is fairly large or beyond practical manufacturing methods. Moreover, it must be removed once it has been in use with a large, heavy duty cone or the like. This requires great force. With moderate or large size seals, a large diameter cone or the like device is required, and this takes considerable force to enter and enlarge the effective inside diameter of the seal. In the alternative, it may be an extremely long, tapered cone, and once again, difficult to remove.
The present invention, however, uses various forms of a simple fixture in which the seal is grasped and then may be readily rotated until the lip takes a temporary set. Alternatively, the fixture may be rotated. Then, the seal is promptly installed before it regains its former dimension of the inside diameter. In this concept, the seal typically may be given several rotations after which the member having contact with the lip may be tightened or forced through a slightly larger inside diameter, and further rotated. This will be determined depending on the thickness of the primary seal or PTFE member, whether there is a primary lip, or a primary lip and a secondary lip, and the degree of deformation required.
It is also very easy to remove the tool used in this application prior to installing the seal. Moreover, the seal forming apparatus is relatively compact, weighing considerably less than a tool otherwise developed for this purpose. Still further, an advantage of this tool is that it may be readily adjustable to various sizes of seal, and accordingly, may be used on different sizes of seals by a very simple adjustment which is provided in the mechanism.
According to one embodiment of the invention, there is provided a frame member which includes two outboard legs and a center section or center leg. Each of these legs is preferably slotted so as to receive the end portion of an axle unit which in turn receives a guide roller, or a forming roller. The guide rollers include laterally outer edges containing ridges or the like and are designed to accommodate the exterior casing of the seal and the forming roller will then work on the lip on the inner diameter of the seal. The apparatus may optimally include a frame for being held down by the foot or the leg of the operator, or may contain another device for mounting the unit on a bench or the like. In use, the seal is simply placed on the two previously adjusted, circumferentially spaced apart guide rollers whose position is determined by moving the axles apart or more together, and thereafter positioning the center roller with whatever tension is desired. The center roller engages the lip and reforms it, more or less as desired by the operator, in stages or in a single stage, using one or preferably several passes of the seal by rotating the casing while the seal is being held in place by the guide rollers.
It is therefore an object of the present invention to provide a new and different method of imparting a temporary deformation of the lip of a resinous seal.
It is another object of the invention to provide such a seal having a simple frame unit which is used to position three rollers.
Another object is to provide a frame having two legs and a center section and having rollers that are adjustable for different sizes and different thicknesses of the primary lip seal.
Another object of the invention is to provide an apparatus which will operate satisfactorily with a single, primary lip and one which will work equally well with seals containing a secondary or dirt lip as well as a primary lip.
A further object of the invention is to provide an apparatus having guide rollers and a reforming roller in which both the guide rollers and the reforming roller may be adjusted, both before and during performing, depending on the circumstances.
It is another object of the invention to provide an apparatus which works well with a large variety of seal inside and outside diameters.
Another object is to provide a smaller device resembling a pliers or the like which may hold and position the rollers used in reforming the seal.
A still further object is to provide a device that may use a variety of attachments to enable the apparatus to be held down or manipulated.
It is still a further object of the invention to provide for a novel method of reforming the lip portion of a seal.